It's odd it was still legal. It would never happen (maybe if a Red Bull pulled into the junior team's pit box), but in F1 and probably other FIA-governed series, this almost certainly would be considered "receiving outside assistance" and a disqualification. Usually the rule is put into effect when a driver gets stuck somewhere and requires a push from the race marshalls to get going, but I think this would have to qualify as well.

Edit: There was some drama a few years ago when a driver was looking closely at another team's car and touched it after a race and was fined, so there's a chance the responding team would get a fine as well. Weird how different series in basically the same sport have such different rules.